蛭石復合功能材料設計合成與性能研究
發(fā)布時間：2018-08-09 16:08
【摘要】：科學技術快速發(fā)展,納米技術有望推動下一次科技革命的誕生。鑒于獨特物理與化學性質,二維結構材料仍然是科技前沿熱點。蛭石作為天然層狀材料,在建筑和農業(yè)等領域具有廣泛應用。但是蛭石功能單一,一直限制其進一步發(fā)展,其真正潛力并沒有凸顯。目前,材料科學研究重心已經轉移到原子、分子以及超分子層次上的納米科學,對納米材料結構與功能的精準調控是關鍵。本論文研究重心放于蛭石結構基本單元蛭石納米片,構建具有不同功能的宏觀組裝體,有助于發(fā)現新材料;同時,將利用膨脹蛭石層狀結構,從微觀上構建具有特定尺寸與形貌的微納結構復合功能材料,并通過雜原子摻雜,實現對材料表面結構調控,實現功能多樣化。本論文主要研究內容如下:(1)首先以原礦為原料制備膨脹蛭石。采用離子溶劑剝離法對膨脹蛭石進行剝離,制備多層或少層蛭石納米片,Zeta電位在-40左右,帶負電,其膠體具有良好的穩(wěn)定性。構建蛭石和水滑石自支撐薄膜,實驗結果顯示蛭石自支撐薄膜具有良好的微納結構,但是在溶液中往往被溶脹所破壞。通過熱淬火處理,在200℃時可以有效抑制其溶脹效應。同時,制備類水滑石CoAl-LDHs納米片膠體溶液,采用LBL方法,實現帶負電天然蛭石和帶正電類水滑石兩類粘土的組裝。(2)充分利用蛭石層板帶負電荷特征,發(fā)揮表面平衡離子Mg2+,Al3+,Ni2+和Ti3+的橋梁作用,在蛭石((Si,Al)O4)四面體和水滑石(AlO6)八面體中間通過氧原子鏈接成鍵(M1-O-M2 (M1 = Mg, Al, Ni or Ti和M2 = Si orAl)),首次實現陽離子型黏土水滑石在陰離子型黏土蛭石表面原位生長,構建多級結構材料。通過第一性原理對其生長機理進行分析,發(fā)現水滑石與蛭石是以晶格匹配方式進行匹配的,且類水滑石將以傾斜方向進行原位生長,這與實驗結果相吻合。源于三維多級結構能夠顯著提高比表面積和傳輸通道,MgAl-LDHs/蛭石復合材料吸附性能顯著提升,與MgAl-LDHs相比,對Cr(Ⅵ)的吸附量提高了 20%; NiTi-LDHs/蛭石復合光催化劑將蛭石強吸附性能和鈦的強催化性能相結合,蛭石的硅基半導體上缺陷位抑制光激發(fā)電子與空穴復合,提高光電子催化效率,加快光電子轉移,降低電子空穴出現幾率,提高可見光的光子吸收,其對亞甲基藍的清除率達到96%,并且它們都具有強的循環(huán)再生性能,其再生率超過90%。(3)采用氣相CVD法,利用碳源和催化劑共裂解,在層狀蛭石層板間原位生長碳納米管,制備具有三明治結構的蛭石/碳納米管復合材料。鑒于碳納米管一般是疏水的,使用前都需要改性,限制了其應用范圍。然而,實驗首次發(fā)現可以在碳納米管制備時,通過改變雜原子摻雜方式,直接調控碳納米管表面原子結構,調節(jié)其親疏水性。研究結果表明,使用二甲苯或三甲苯為碳源,可以制備超疏水碳納米管(CA=158.1),使用吡啶作為碳源,可以制備超親水碳納米管(CA=0)。(4)以制備的超親水性碳納米管為原料,利用簡單的自吸附和冷凍干燥輔助固定方法,在其表面上均勻負載Co3O4納米顆粒,構建雙功能催化劑。雜原子摻雜碳納米管和均勻分布的氧化鈷納米顆粒賦予所獲得的Co3O4/碳納米管復合材料具有良好的OER和ORR性能。在此基礎上,以均勻負載CoFeOx納米顆粒的碳納米管為原料,利用上面負載的CoFeOx作為催化劑,采用雙氰胺為碳源和氮源,通過固體CVD法在其上生長高氮含量的碳納米管和石墨烯,制備碳納米管/石墨烯/過渡金屬組成的復合功能材料。關鍵是在制備過程中過渡金屬氧化物納米顆粒直接轉化為金屬,并且其均勻地分散在該復合材料中,并被薄碳膜包裹,能提供更多活性位點。碳納米管/石墨烯/過渡金屬組成的復合功能材料的ORR(-3 mA/cm2)和OER (10 mA/cm2)之間的過電壓之差為0.845,因此該材料是一種優(yōu)異的雙功能催化劑。(5)實驗研究發(fā)現摻雜的碳納米管和石墨烯,其結構和表面會產生很多晶格缺陷,少層碳包裹的金屬納米顆粒,會改變原有sp2雜化碳層的結構,加速電子轉移,都會促進形成催化活性位點。本實驗結果顯示,隨著摻氮含量增加,不僅可以用于OER和ORR的電催化性能,其電容性能也在增加。
[Abstract]:With the rapid development of science and technology, nanotechnology is expected to promote the birth of the next scientific and technological revolution. In view of its unique physical and chemical properties, the two-dimensional structure material is still a hot spot in the frontier of science and technology. Vermiculite as a natural layered material has been widely used in the fields of architecture and agriculture. However, the function of vermiculite has been limited and its further development has been limited. The center of material science has shifted to atomic, molecular and supramolecular Sciences, and the key to the precise regulation of the structure and function of nanomaterials is the key. This paper is focused on the vermiculite nanoplates of the vermiculite structure and the construction of macro assemblies with different functions. At the same time, we will use the layered structure of the expanded vermiculite to construct microstructural composite functional materials with specific size and morphology from the microcosmic, and to control the surface structure of the material by doping the heteroatom, and realize the diversification of the function. The main contents of this paper are as follows: (1) first of all, the expanded vermiculite is prepared with raw ore as raw material. By stripping the expanded vermiculite by ionic solvent stripping, multilayer or less layer vermiculite nanoscale was prepared. The Zeta potential was about -40, with negative electricity, and the colloid had good stability. The self supporting film of vermiculite and hydrotalcite was constructed. The experimental results show that the self supporting film of vermiculite has good micro nano structure, but it is often swelling in solution. By heat quenching, the swelling effect can be effectively suppressed at 200 c. At the same time, the colloidal solution of the hydrotalcite CoAl-LDHs nanoscale is prepared and the LBL method is used to assemble the negative charged natural vermiculite and the two types of clay with positive hydrotalcite. (2) the negative charge characteristics of the leech layer are fully utilized, and the surface equilibrium ion Mg2+, A L3+, Ni2+ and Ti3+ are used to bridge the surface of the vermiculite ((Si, Al) O4) tetrahedron and water talcum (AlO6) eight surface by linking oxygen atoms to bond (M1-O-M2 (M1 = Mg, Al, Ni)) for the first time to build the surface of the anionic clay vermiculite surface and construct a multi-stage structure material. The growth mechanism of the water talcum and vermiculite is matched by the lattice matching method, and the water like talcum will grow in the inclined direction. This is in agreement with the experimental results. The specific surface area and transmission channel can be significantly improved from the three-dimensional multistage structure. The adsorption performance of MgAl-LDHs/ vermiculite composite material is significantly raised. Compared with MgAl-LDHs, the adsorption capacity of Cr (VI) was increased by 20%, and the NiTi-LDHs/ vermiculite composite photocatalyst combined the strong adsorption properties of vermiculite with the strong catalytic properties of titanium. The defect positions on the vermiculite silicon based semiconductor inhibited the recombination of light excited electrons and holes, enhanced the efficiency of photoelectron catalysis, accelerated the photoelectron transfer and reduced the appearance of electron hole. Probability, enhanced photons absorption of visible light, and its clearance rate to methylene blue reached 96%, and they all had strong recycling performance, and their regeneration rate was more than 90%. (3) using gas phase CVD method. Carbon nanotubes were grown by carbon source and catalyst, and sandwiched vermiculite / carbon nanostructures were prepared in sandwich structure. Tube composites. Since carbon nanotubes are generally hydrophobic, they need to be modified before use, limiting their application. However, for the first time, experiments have been found that the surface atomic structure of carbon nanotubes can be directly regulated by changing the doping method of hetero atoms to regulate the hydrophobicity of carbon nanotubes. The results show that the use of xylene or three is used. Super hydrophobic carbon nanotubes (CA=158.1) can be prepared as carbon source, and super hydrophilic carbon nanotubes (CA=0) can be prepared by using pyridine as a carbon source. (4) super hydrophilic carbon nanotubes are prepared by using simple self adsorption and freeze-drying assisted immobilization methods, and Co3O4 nanoparticles are loaded evenly on the surface of the nanotube, and the dual function catalysis is constructed. The doped carbon nanotubes and the uniformly distributed cobalt oxide nanoparticles give the obtained Co3O4/ carbon nanotube composites a good OER and ORR properties. On this basis, the carbon nanotubes loaded with CoFeOx nanoparticles are used as the raw materials and the CoFeOx as the catalyst is used as the catalyst, and dicyandiamide as the carbon source and nitrogen source. A composite functional material composed of carbon nanotubes / graphene / transition metal is prepared by the solid CVD method, and the key is that the transition metal oxide nanoparticles are directly converted into metal in the preparation process, and they are evenly dispersed in the composite and are encapsulated by thin carbon films and can be extracted. For more active sites. The difference in overvoltage between ORR (-3 mA/cm2) and OER (10 mA/cm2) of carbon nanotubes / graphene / transition metals is 0.845, so the material is an excellent bifunctional catalyst. (5) experimental studies have found that doped carbon nanoscale and graphene, its structure and surface will produce a lot of lattice. Defects, small carbon coated metal nanoparticles will change the structure of the original SP2 hybrid carbon layer and accelerate the electron transfer, which can promote the formation of catalytic active sites. The results show that with the increase of nitrogen content, the electrocatalytic properties of OER and ORR are not only used, but their electrical capacity is also increased.
【學位授予單位】：北京化工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB34;O643.36
本文編號：2174624
[Abstract]:With the rapid development of science and technology, nanotechnology is expected to promote the birth of the next scientific and technological revolution. In view of its unique physical and chemical properties, the two-dimensional structure material is still a hot spot in the frontier of science and technology. Vermiculite as a natural layered material has been widely used in the fields of architecture and agriculture. However, the function of vermiculite has been limited and its further development has been limited. The center of material science has shifted to atomic, molecular and supramolecular Sciences, and the key to the precise regulation of the structure and function of nanomaterials is the key. This paper is focused on the vermiculite nanoplates of the vermiculite structure and the construction of macro assemblies with different functions. At the same time, we will use the layered structure of the expanded vermiculite to construct microstructural composite functional materials with specific size and morphology from the microcosmic, and to control the surface structure of the material by doping the heteroatom, and realize the diversification of the function. The main contents of this paper are as follows: (1) first of all, the expanded vermiculite is prepared with raw ore as raw material. By stripping the expanded vermiculite by ionic solvent stripping, multilayer or less layer vermiculite nanoscale was prepared. The Zeta potential was about -40, with negative electricity, and the colloid had good stability. The self supporting film of vermiculite and hydrotalcite was constructed. The experimental results show that the self supporting film of vermiculite has good micro nano structure, but it is often swelling in solution. By heat quenching, the swelling effect can be effectively suppressed at 200 c. At the same time, the colloidal solution of the hydrotalcite CoAl-LDHs nanoscale is prepared and the LBL method is used to assemble the negative charged natural vermiculite and the two types of clay with positive hydrotalcite. (2) the negative charge characteristics of the leech layer are fully utilized, and the surface equilibrium ion Mg2+, A L3+, Ni2+ and Ti3+ are used to bridge the surface of the vermiculite ((Si, Al) O4) tetrahedron and water talcum (AlO6) eight surface by linking oxygen atoms to bond (M1-O-M2 (M1 = Mg, Al, Ni)) for the first time to build the surface of the anionic clay vermiculite surface and construct a multi-stage structure material. The growth mechanism of the water talcum and vermiculite is matched by the lattice matching method, and the water like talcum will grow in the inclined direction. This is in agreement with the experimental results. The specific surface area and transmission channel can be significantly improved from the three-dimensional multistage structure. The adsorption performance of MgAl-LDHs/ vermiculite composite material is significantly raised. Compared with MgAl-LDHs, the adsorption capacity of Cr (VI) was increased by 20%, and the NiTi-LDHs/ vermiculite composite photocatalyst combined the strong adsorption properties of vermiculite with the strong catalytic properties of titanium. The defect positions on the vermiculite silicon based semiconductor inhibited the recombination of light excited electrons and holes, enhanced the efficiency of photoelectron catalysis, accelerated the photoelectron transfer and reduced the appearance of electron hole. Probability, enhanced photons absorption of visible light, and its clearance rate to methylene blue reached 96%, and they all had strong recycling performance, and their regeneration rate was more than 90%. (3) using gas phase CVD method. Carbon nanotubes were grown by carbon source and catalyst, and sandwiched vermiculite / carbon nanostructures were prepared in sandwich structure. Tube composites. Since carbon nanotubes are generally hydrophobic, they need to be modified before use, limiting their application. However, for the first time, experiments have been found that the surface atomic structure of carbon nanotubes can be directly regulated by changing the doping method of hetero atoms to regulate the hydrophobicity of carbon nanotubes. The results show that the use of xylene or three is used. Super hydrophobic carbon nanotubes (CA=158.1) can be prepared as carbon source, and super hydrophilic carbon nanotubes (CA=0) can be prepared by using pyridine as a carbon source. (4) super hydrophilic carbon nanotubes are prepared by using simple self adsorption and freeze-drying assisted immobilization methods, and Co3O4 nanoparticles are loaded evenly on the surface of the nanotube, and the dual function catalysis is constructed. The doped carbon nanotubes and the uniformly distributed cobalt oxide nanoparticles give the obtained Co3O4/ carbon nanotube composites a good OER and ORR properties. On this basis, the carbon nanotubes loaded with CoFeOx nanoparticles are used as the raw materials and the CoFeOx as the catalyst is used as the catalyst, and dicyandiamide as the carbon source and nitrogen source. A composite functional material composed of carbon nanotubes / graphene / transition metal is prepared by the solid CVD method, and the key is that the transition metal oxide nanoparticles are directly converted into metal in the preparation process, and they are evenly dispersed in the composite and are encapsulated by thin carbon films and can be extracted. For more active sites. The difference in overvoltage between ORR (-3 mA/cm2) and OER (10 mA/cm2) of carbon nanotubes / graphene / transition metals is 0.845, so the material is an excellent bifunctional catalyst. (5) experimental studies have found that doped carbon nanoscale and graphene, its structure and surface will produce a lot of lattice. Defects, small carbon coated metal nanoparticles will change the structure of the original SP2 hybrid carbon layer and accelerate the electron transfer, which can promote the formation of catalytic active sites. The results show that with the increase of nitrogen content, the electrocatalytic properties of OER and ORR are not only used, but their electrical capacity is also increased.
【學位授予單位】：北京化工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB34;O643.36
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